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The Mount Bruce Megasequence Set (formerly the Mount Bruce Supergroup) was deposited on the Pilbara Craton during the late Archaean and early Proterozoic. It comprises two megasequences, the Chichester Range Megasequence and the overlying Hamersley Range Megasequence. Each megasequence comprises three supersequences or supersequence packages whose tectonic history can be explained in terms of Phanerozoic-style tectonics. The basal Nullagine Supersequence, which comprises mostly subaerial basalt and terrigenous sedimentary rock, was deposited during an episode of WNW-ESE directed crustal extension that was initiated at about 2770 Ma. The overlying Mount Jope Supersequence, which comprises mostly basalt and tuff, was deposited during the subsequent development of a WNW-ESE trending rift before about 2690 Ma. Mudrock, carbonate sedimentary rock and iron formation in the overlying circa 2690 to circa 2600 Ma Marra Mamba Supersequence Package were deposited on the ensuing divergent craton margin. An unconformity or condensed succession covering a time span of as much as 130 m.y. separates the top of the Chichester Range Megasequence from the Hamersley Range Megasequence during which time an oceanic island arc is interpreted to have collided with the southern Pilbara Craton margin. Subsequently, the subducting oceanic plate flipped from southwest dipping to northeast dipping, and convergence resulted in the formation of a marginal subduction-related orogen with associated arc and backarc volcanism. Iron formation and distal arc-derived tuffs of the Brockman Supersequence Package were deposited on a siliciclastic-starved platform in a neutral continental backarc setting at around 2470 Ma. The overlying circa 2440 Ma Woongarra Supersequence was also deposited in a backarc continental setting and comprises iron formation, felsic tuffs, and probably coeval mafic rocks. The latter two rocks types were derived from a backarc magmatic belt. Shortening of the southern Pilbara Craton margin resulted in the development of a backarc compressive cratonic basin in which iron formation and siliciclastic and carbonate sedimentary rock of the Turee Creek Supersequence were deposited, and ultimately resulted in a continent-continent collision. The Mount Bruce Megasequence Set and its contained iron formations are preserved in the relatively distal hinterland of this collisional orogen.

Situated south of the eastern Himalayan syntaxis at the western margin of the Shan-Thai terrane the highgrade Mogok metamorphic belt (MMB) in Myanmar occupies a key position in the tectonic evolution of Southeast Asia. The first sensitive high-resolution ion microprobe U-Pb in zircon geochronology for the MMB shows that strongly deformed granitic orthogneisses near Mandalay contain Jurassic (~170 Ma) zircons that have partly recrystallized during ~43 Ma high-grade metamorphism. A hornblende syenite from Mandalay Hill also contains Jurassic zircons with evidence of Eocene metamorphic recrystallization rimmed by thin zones of 30.9 plus or minus 0.7 Ma magmatic zircon. The relative abundance of Jurassic zircons in these rocks is consistent with suggestions that southern Eurasia had an Andean-type margin at that time. Mid- Cretaceous to earliest Eocene (120 to 50 Ma) I-type granitoids in the MMB, Myeik Archipelago, and Western Myanmar confirm that prior to the collision of India, an up to 200 km wide magmatic belt extended along the Eurasian margin from Pakistan to Sumatra. Metamorphic overgrowths to zircons in the orthogneiss near Mandalay date a period of Eocene (~43 Ma) high-grade metamorphism possibly during crustal thickening related to the initial collision between India and Eurasia (at 65 to 55 Ma). This was followed by emplacement of syntectonic hornblende syenites and leucogranites between 35 and 23 Ma. Similar syntectonic syenites and leucogranites intruded the Ailao Shan-Red River shear belt in southern China and Vietnam during the Eocene-Oligocene to Miocene, and the Wang Chao and Three Pagodas faults in northern Thailand (that most likely link with the MMB) were also active at this time. The complex history of Eocene to early Miocene metamorphism, deformation, and magmatism in the MMB provides evidence that it may have played a key role in the network of deformation zones that accommodated strain during the northwards movement of India and resulting extrusion or rotation of Indochina.

[1] The establishment of an oxygen-rich atmosphere dramatically altered the evolution of life on Earth. Most of the recent discussion of the topic has been focused on the timing of the event rather than on its mechanism. Here we draw upon recent developments in the understanding of Earth's interior to propose that the rise of oxygen followed a geologically abrupt period of mantle overturn and/or intense plume activity near the Archean-Proterozoic transition, 2470–2450 million years ago. The magmatic event has already been linked to the widespread deposition of oxide-facies banded iron formation, and the rise of oxygen has been implicated as the trigger for iron deposition and Earth's first major glaciation. We argue that these events are all related to a change in redox state of volcanic gases brought about by deep-seated Late Archean and earliest Paleoproterozoic magmatism.